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Parameters predictors of the iridocorneal angle after implantable collamer lens surgery

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First Author: S.Cerpa Manito SPAIN

Co Author(s):    A. Sánchez Trancón   O. Torrado Sierra   A. Baptista   P. Serra           

Abstract Details

Purpose:

The implantation of an Implantable Collamer Lens (ICL) implies the correction of the refractive error with the absence or minimal affection of the intraocular physiological mechanisms after surgery so that the eye can maintain its normal functioning. One of these mechanisms is the regulation of the aqueous humour outflow through the trabecular meshwork which requires the maintenance of a certain iridocorneal angle (ICA) aperture. Previous studies have shown the reduction in ICA aperture after ICL implantation. This study aims to identify the parameters regulating the postoperative-ICA after ICL surgery.

Setting:

Ophthalmology Clinic Vista Sánchez Trancón, Badajoz, Spain

Methods:

This retrospective case series analyzed 225 eyes (225 patients) implanted with myopic ICL (STAAR EVO-V4c, size:13.2mm). Scheimpflug-tomography was used for measuring: white-to-white (WTW), central keratometry (Kc) and central corneal thickness (CCT). Anterior-segment OCT was applied for measuring: iridocorneal angle-to-angle (ATA), internal anterior chamber (ACQ), crystalline lens rise (CLR), iridocorneal angle (ICA) and vault. Bivariate correlation analysis was used to identify parameters correlated with postoperative-ICA. Postoperative-ICA was correlated to preoperative-ICA, ACQ, CLR, and vault. Eyes were classified in accordance with their anterior-segment biometry using cluster analysis. Finally, the effect of the vault on postoperative-ICA determined through linear regression for each cluster.

Results:

Postoperative-ICA was correlated to preoperative-ICA (R=0.485), ACQ (R=0.310), CLR (R=-0.140) and Vault (R=-0.491). The anterior-segment clustering segmented the sample in three groups using the ACQ and preoperative-ICA as predictors (Cluster_1: ACQ=3.27mm, Preoperative-ICA=34.60deg; Cluster_2: ACQ=3.27mm, Preoperative-ICA=39.60deg; Cluster_3: ACQ=3.52mm, Preoperative-ICA=49.94deg). The vault, postoperative-ICA and mount of angle closure differed between these groups. The postoperative-ICAs were wider in eyes presenting deeper ACQ and wider preoperative-ICA; angle closure was more accentuated in eyes with deeper ACQs and wider preoperative-ICAs. Linear regression analysis on the three clusters indicated that an ICL produces a baseline reduction in ICA and a variable reduction depending on the vault.

Conclusions:

The postoperative-ICA depends on the anterior-segment anatomy, in particular, the ACQ and preoperative angle, and on the vault magnitude. Implanting an ICL produces a baseline reduction in the ICA (estimated as 9.0 to 16.0 deg) plus an additional reduction of 0.6 to 1.0 deg per every 100 μm of vault increase. These findings have two major implications, one the preoperative-ICA needs to be assessed prior surgery and interpreted along with the ACQ amplitude, and two an estimation of the vault needs to be made to account for the contribution of the vault in the ICA reduction.

Financial Disclosure:

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